Only the owner has the right to enjoy and dispose of his or her property, save when the law permits such disposition to be made through an authorized representative. (Article 428 in relation to Article 1878 (5), New Civil Code of the Philippines)
Correspondingly, a person can be sued for estafa if, despite knowing that he or she is neither the owner nor the latter's authorized representative, said person represents one's self as possessing the right or authority to sell a property and eventually sells it to a buyer who relied on such false representation and in due course suffered damages.
Such a manner of swindling is penalized under our law under the following provision:
"Art. 315. Swindling (estafa).— Any person who shall defraud another by any of the means mentioned hereinbelow:
"2. By means of any of the following false pretenses or fraudulent acts executed prior to or simultaneously with the commission of the fraud:
"(a) By using fictitious name, or falsely pretending to possess power, influence, qualifications, property, credit, agency, business or imaginary transactions, or by means of other similar deceits." (Article 315 (2)(a), Revised Penal Code, as amended by Republic Act 10951)
It is to be expected that a person who committed a crime, such as estafa, will raise any and all available defenses, which include the assertion of negligence or lack of diligence on the part of the victim. Failure to act with due diligence is generally disadvantageous and prejudicial, and often causes injury or damage to a concerned party.
But if said party earnestly relied on the declarations and assurances given to him/her, and deceit or fraud was in fact committed by the offender, then such failure to exercise due diligence will not shield the offender from criminal responsibility. The Supreme Court, through Associate Justice Ramon Paul Hernando, elucidated in the case of Spouses Isidro Dulay 3rd and Elena Dulay vs. People of the Philippines (GR 215132, Sept. 13, 2021) the following:
"We note that private complainants do not appear to have conducted due diligence in ascertaining actual ownership of the property. However, private complainants' failure to conduct due diligence does not negate petitioners' fraud in pretending to own the subject property and gain by selling it to gullible buyers.
In short, the estafa by deceit was consummated when petitioners received payments for the subject property knowing that they were not the registered owners who could validly transfer title thereto. Time and again we have ruled that the one induced, who must be ignorant of the falsity of the representations, must have relied on the truth thereof and, as a consequence, sustained injury.
"In Virata v. Ng Wee, we defined "fraud" as the voluntary execution of a wrongful act, or a willful omission, knowing and intending the effects which naturally and necessarily arise from such act or omission. In its general sense, fraud is deemed to comprise anything calculated to deceive, including all acts and omissions and concealment involving a breach of legal or ethical duty, trust, or confidence justly reposed, resulting in damage to another, or by which an undue and unconscientious advantage is taken of another. Fraud is also described as embracing all multifarious means which human ingenuity can device, and which are resorted to by one individual to secure an advantage over another by false suggestions or by suppression of truth and includes all surprise, trick, cunning, dissembling, and any unfair way by which another is cheated."
As a victim you should pursue filing a complaint for estafa against the seller who sold you such a property, provided that one can clearly establish that said seller has no right or authority to sell the same, that one bought the property genuinely relying on the representations of the seller, which eventually turned out to be false, and that one in fact suffered damages by reason thereof.